The Leyland cypress (x Cupressocyparis leylandii ) is a hybrid of the stately Monterey cypress and the Alaskan cedar. A versatile tree, it is used as a Christmas tree in the U.S., as an ornamental in the U.K. and for its wood in Australia. One of the interesting aspects of the Leyland cypress is that it secretes a substance that is toxic to other plants, so nothing will grow beneath it. If you are planting a young Leyland cypress, keep in mind that this tree is expected to grow to a height of 138 feet, so don't plant it under any low-hanging powerlines.
Provide your Leyland cypress tree with full sun, all day.
Water the Leyland cypress slowly and deeply. Drip irrigation is the recommended application process. A soaker hose will also work well. How often you need to water the tree will depend upon the weather in your region. If it is dry, water deeply (to a depth of eight inches) every two weeks.
Fertilize the Leyland cypress tree annually, in early spring with an eight- to nine-month time-release, 18-8-8 formula.
Pull any weeds or grass growing in the root zone of the Leyland cypress. Because this tree has a shallow root system, competition for water and nutrients can be detrimental to it. Adding a three-inch layer of mulch around the base of the Leyland cypress (don't allow the mulch to touch the bark of the tree) and spreading it out to a distance of three feet, will help to discourage weeds.
Inspect the Leyland cypress for pests. Bagworms, scale and spider mites are all attracted to the tree. The bagworms can be picked off by hand, but treat scale with an insecticide, and spider mite infestations require applications of miticide. Your county cooperative extension agent can assist you in finding the appropriate product for use in your area.
Check the Leyland cypress for signs of disease. Symptoms include yellowing needles that fall to the ground and dead or dying branches. The two major diseases that affect the Leyland Cypress are canker and blight. There is no chemical treatment for canker and fungicide is effective against the fungi that causes blight. Consult your county cooperative extension agent for which products are most effective in your climate and region.
Prune your Leyland cypress to control the height or to shape it into hedging. For hedges, begin pruning the Leyland cypress when it reaches three feet in height. Cut only the sides of the plant and don't take any more than three to four inches of growth. After pruning, spray the tree with a fungicide every week for six weeks.